30 THE NON-MARINE MOLLUSCS OF ESSEX.
Walden district, belongs in reality to the river system of
Cambridgeshire. Localities for the species are given under
these three headings, and are followed in all cases by the name or
initials of the authority for them, or of the museum in which the
specimens are preserved.
LIST OF THE NON-MARINE MOLLUSCS OF ESSEX.
Distribution.
A. South and West Essex ; valleys of the rivers Lea, Roding,
and Crouch.
B. Central Essex ; valleys of the rivers Blackwater (Chelmer)
and Colne.
C. North Essex ; valleys of the rivers Stour and Brook.
Classification.
The general classification is according to Lang's Text-book
of Comparative Anatomy, English edition, part ii. (1896); the
families are those given by Fischer in his Manuel de Conchylio-
logie, and the generic names adopted by Pilsbry in his Guide
to the Study of the Helices have been used ; while in order
that the species which do not occur in the county may be noted,
all the British species have been given.
Signs and Abbreviations.
If the name of a species he placed within square brackets, it
signifies that the form has hitherto heen found in Essex only in a fossil
state ; if, further, the name be in lighter type, the species is not known
to occur in the county.
An asterisk (*) denotes that specimens are in the possession of the
Essex Field Club: a dagger (†) signifies an addition to, a double dagger (‡)
a correction in, a published list.
Records for fossils are printed in italics. Fossils that have not
heen recorded by B. B. Woodward, or which have not been determined by
him, A. S. Kennard, or the writer, are placed within square brackets.
C.S.R. ... ... Conchological Society's Authenticated
Records.
E.N. ... ... Essex Naturalist.
K. and W. ... Kennard and Woodward.
S.W. Museum ... Saffron Walden Museum.
W.M.W. ... The Writer.